1-Pathology:a) DecaySpecial types of oral bacteria cause demineralization and destruction of the hard tissues of the teeth (enamel, dentin, and cementum). According on the extent of tooth destruction, various treatments can be used to restore teeth to proper form, an extraction can also serve as treatment for dental caries. The removal of the decayed tooth is performed if the tooth is extensively destroyed from the decay process such that it is not possible to effectively restore the tooth.

b) Periodontal problem (gum problems)Periodontal diseases range from simple gum inflammation to serious disease that results in major damage to the soft tissue and bone that support the teeth. When gingivitis is not treated, it can advance to "periodontitis". In periodontitis, gums pull away from the teeth and form spaces (pocket) that become infected. The body's immune system fights the bacteria as the plaque spreads and grows below the gum. Bacterial toxins, and the body's natural response to infection, start to destroy the bone and connective tissue that hold teeth in place. If not treated, the bones, gums, and tissue that support the teeth are destroyed. The teeth may eventually become mobile and have to be extracted.

c) Cystic lesionOral cystic lesion may be of dental or non-dental origin, some of them infectious or non-infectious lesion. When the cystic lesion is associated with a tooth, this lead to non-vitality of the tooth, and bone destruction (due to cyst expansion) around the tooth, leading to its mobility. All these factors give an indication to remove the tooth, especially when the origin of the cyst is from the tooth itself.

d) Tumor lesionTumor lesion has the same scenario with cystic lesion, due to tumor expansion that leads to bone destruction, teeth mobility and flaring up. Most of the time complete excision of the tumor is necessary, and this may include jaw bone and the teeth involved.

e) PericoronitisPericoronitis is an inflammatory condition that involves partially erupted teeth, and is very common in wisdom tooth. The gingival collar around the tooth will be swollen, tender, and red in color. This condition is related to food impaction between the partially erupted tooth and gingiva surrounding it, and due to difficulty in keeping the area clean from the impacted food, leading gum inflammation. When the condition becomes recurrent (more than one episode in few months), and the tooth does not erupt, in this case partially erupted tooth, it is advised for extraction to avoid serious infection (Ludwig's angina).

2-Traumaa) Tooth fractureTooth fracture can involve only the enamel, enamel with dentin, or enamel with dentin and root structure; the last type being difficult to treat even with root canal treatment, due to incomplete sealing of the restoration that may lead to leakage and root canal treatment failures. In this case, tooth extraction is indicated.

b) Jaw fractureWhen facial trauma cause maxillary or mandibular fracture, the line of the fracture sometimes include dental area and cause tooth fracture (compound fracture). In this case, the tooth should be removed surgically to avoid bone loss in the fracture line.

3-Orthodontic demandTeeth crowding is the most common reason that people seek orthodontic treatment for. Teeth crowding is caused by discrepancy between the size of the jaw, or the dental arch, and the size of the teeth crown. So, space is needed to realign the teeth into their normal position; the space will be created by removing teeth. Most of the time the teeth removed in orthodontic treatment is the first premolar and second premolar. Before the orthodontic treatment starts, teeth that cannot be restored or has poor prognosis should be removed (supernumerary teeth as well), as this may affect the treatment plan. Impacted teeth (bony impaction) should be removed, since this may affect the teeth movement during orthodontic treatment

4-Prosthetic demandUnsavable teeth, or unrestorable teeth, should be removed before starting with any prosthetic treatment, as this may affect the treatment plan and extension of the prostheses to include the unrestorable teeth (or not). Questionable teeth during the treatment plan should be decided to be maintained or removed, especially when these teeth form an abutment for future prostheses, as removing these teeth after prostheses issuing will be more problematic.

5-Endodontic reasonEndodontically treated teeth are prone to extraction, mainly due to non-restorable carious destruction; and to a lesser extent, to endodontic-related reasons, such as endodontic failure, iatrogenic perforation, or cracked roots. Some teeth are difficult to treat with root canal treatment due to root canal blockage, or severely curved roots. Sometimes, the tooth is involved with perio-endodontic problem with severe bone destruction; all these indicates removal of the tooth, rather than maintain it

6-Impacted teethAny tooth in the dental arch is subject to impaction (unerupted), but it is more common in wisdom teeth (as it is the last teeth to be erupted). Sometimes, the impacted teeth are not causing any problem to the patient, or there is no clinical indication to remove it. But in case of recurrent infection, problems caused to the adjacent teeth, or there is orthodontic or prosthetic demand to remove the impacted tooth, surgery should be planned to remove it, without any trauma to the vital structure (nerve, blood vessels and maxillary sinus) or adjacent teeth.

7-Misaligned toothWhen the tooth is not erupted with the dental arch (erupted more buccally or lingually), and has improper contact with adjacent teeth, the tooth consider as misaligned. Misaligned tooth will cause decay and periodontal problem to the adjacent teeth, due to difficulty to access and clean the area (more common on the premolar area). Misaligned tooth is usually treated with orthodontic treatment, but sometimes the tooth is severely rotated or inclined that it is difficult to correct with orthodontic treatment, or the tooth is unrestorable and badly decayed, in this case the tooth is decided to be removed.

8-Unrestorable toothAs mentioned earlier, the unrestorable tooth is always sacrificed and removed. But who will decide whether the tooth is restorable or not? Tooth restorations always get support and retention from the tooth structure; when the tooth structure is destroyed from decay or trauma, the restoration prognosis would be poor, and there is slim chance for the restoration to last. Most of these cases need root canal treatment, so the prognosis should be estimated and weighted against tooth removal. As root canal treatment will cost time and money for the patient, and still the tooth will be susceptible to decay in the future, maybe more than one opinion is needed to evaluate the tooth condition before any decision is taken.

9-Supernumerary teethA supernumerary tooth is one that is additional to the normal series and can be found in almost any region of the dental arch. The most common supernumerary tooth which appears in the maxillary midline is called a mesiodens. There are many indications to remove the supernumerary teeth that can be summarized with: central incisor eruption that has been delayed or inhibited, altered eruption or displacement of central incisors is evident, there is associated pathology, and active orthodontic alignment.

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Factors that might contribute:There are some factors that might contribute directly or indirectly on the incidence and causes of the tooth extraction

AgeThe incidence of tooth decay is high among the youngster and below the age of 25 years old, with advance age the incidence of the tooth decay start to decrease and the incidence of the periodontal problem (gum disease) start to increase. So, most of causes of tooth extraction below the age 30 years is due to dental decay, while above this age tooth is sacrificed due to periodontal problem

Place of livingWater fluoridation is crucial in the increase of the tooth resistance against decay. Some of the developed country started this plan more than decade ago, and the result is significant decrease in the incidence of tooth decay. Consequentially, the tooth extraction due to tooth decay decreased dramatically.

Patient and dentist orientationWe can observe that uninformed, or unaware, patient has less intention to preserve the tooth, rather than to remove it. In such case, the patient should be informed about the consequences and the drawback of tooth extraction before proceeding with it. On the other hand, we can find some of dentist more oriented toward tooth extraction rather than preservation. This may be due to lack of skills or experience in the performance of advanced or specialized dental treatments.

RaceA study done by Tuft University showed that the Asian population has thin biotype gingiva, and the periodontium is less resistant to the bacterial infection. For this reason, we can observe high incidence of periodontal disease among Asian population, and most tooth removal is due to gum disease, and tooth mobility.

Tooth positionSome of the teeth are more susceptible to dental caries than the others due to early eruption, such as first molars. As these teeth are the first permanent teeth erupting into the oral cavity, most of the time, they are missing or heavily restored. Meanwhile, anterior teeth are more susceptible to be lost due to trauma.

Incomplete treatmentFear of the dental treatment cause most of the patients to not turn up or complete their treatments. Teeth with temporary filling, or root canal treatment with incomplete sealed filling, make the tooth structure more susceptible to caries and fracture.

FinanceDental treatment is considered costly for most patients, especially for the long and complicated treatments. This factor cause most patients to seek for cheap and fast treatments. Complex tooth restoration and root canal treatment considered as high cost dental treatment, in comparison to the tooth extraction. For this reason, we can find more missing teeth among low income people.